This project will investigate the two basic tenets of behavioral medicine: that environmental events and their psychophysiological consequences can produce organic disease and that environmental treatments which alter psychophysiological processes can cure or ameliorate disease. This project will determine whether stress alone can produce potentially lethal disease or whether the stress must be administered to an organism with a predisposition to serious disease or whether the stress must be administered to an organism with a predisposition to serious disease. It will determine whether there are differences in the frequency and severity of stress-induced heart failure in cardiomyopathic hamsters (CMHs) and healthy hamsters (HHs). It will provide a profile of physiological processes during the development of stress-induced heart failure in CMHs and HHs. It will examine the relationship of predisposition and stress intensity to disease, and it will examine differences between CMHs and HHs in their response to stress. This project will develop an important, new model for studying the roles of stress and predisposition in the development of serious, life-threatening disease. This project will also investigate a new environmental treatment, chronotherapy. Chronotherapy involves altering the organism's circadian rhythms to produce beneficial effects. My preliminary studies show that chronotherapy can profoundly alter susceptibility to stressinduced disease. This project will use the cardiomyopathic hamster model to investigate the effectiveness of stress-induced chronotherapy as a treatment for stress-induced heart failure. It will survey the effects of three chronotherapeutic schedules on the frequency or severity of stress-induced heart failure. It will determine whether chronotherapy alters the profile of physiological changes following stress. It will examine the effects of chronotherapy on the predisposition-stress-disease relationship, and it will determine whether chronotherapy could exert its beneficial effects by reducing the response to stress. This project will take the first steps towards understanding and developing chronotherapy as a new, non-pharmacological mode of therapy.